Cysteine protease is a generic name of proteases which have a cysteine residue in the activity center and catalyze protein degradation thereat. In animal cells, a large number of cysteine proteases are known; for example, cathepsin family, calpain family, caspase-1, etc. Cysteine protease exists in various kinds of cells extensively and plays a basic and essential role in the homeostasis, such as conversion (processing) of precursor protein into its active form and degradation of proteins which have become out of use, etc. Until now, its physiological effects are being vigorously studied, and as the studies progress and characteristics of the enzymes are revealed, cysteine protease came to be taken as a cause of really various kinds of diseases.
It is revealed that cathepsin S (See J. Immunol., 161, 2731 (1998)) and cathepsin L (See J. Exp. Med., 183, 1331 (1996)) play a role in processing of major histocompatibility antigen class-II in antigen presenting cells which play an important role in the early stage of immune responses. In an experimental inflammatory response model induced by antigens, a specific inhibitor of cathepsin S showed an inhibitory effect (see J. Clin. Invest., 101, 2351 (1998)). It is also reported that in a leishmania-infected immune response model cathepsin B inhibitor inhibited an immune response and by means of this effect it inhibited the proliferation of protozoans (See J. Immunol., 161, 2120 (1998)). In vitro, a result is given that a calpain inhibitor and a cysteine protease inhibitor E-64 inhibited apoptosis which is induced by stimuli on T cell receptors (see J. Exp. Med., 178, 1693 (1993)). Therefore, it is conceivable that cysteine protease is much concerned with the progress of immune responses.
It is speculated that caspase-1 or a cysteine protease similar thereto occupies an important position in the mechanism of cell death including apoptosis. Therefore it is expected for a cysteine protease inhibitor to be used as an agent for the prophylaxis and/or treatment of those diseases concerning apoptosis, such as infectious diseases, deterioration or sthenia of immune function and brain function, tumors, etc. Diseases concerning apoptosis are, acquired immune deficiency syndrome (AIDS), AIDS-related complex (ARC), adult T cell leukemia, hairy cell leukemia, spondylopathy, respiratory apparatus disorder, arthitis, HIV or HTLV-1 related diseases such as uveitis, virus-related diseases such as hepatitis C, cancer, collagenosis (systemic lupus erythematosus, rheumatoid arthritis, etc.), autoimmune diseases (ulcerative colitis, Sjögren's syndrome, primary biliary cirrhosis, spontaneous thrombocytopenic purpura, autoimmune hemolytic anemia, myasthenia gravis, insulin dependent (type I) diabetes, etc.), diseases accompanied by thrombocytopenia (osteomyelodysplasia syndrome, periodic thrombocytopenia, aplastic anemia, spontaneous thrombocytopenia, disseminated intravascular coagulation (DIC), etc.), hepatic diseases such as viral hepatitis (type C, A, B, F, etc.) or hepatitis medicamentosus and cirrhosis, dementia (Alzheimer's diseases, Alzheimer's senile dementia, etc.), cerebrovascular injury, nerve degeneration diseases, adult acute respiratory distress syndrome, infectious diseases, prostatomegaly, hysteromyoma, bronchial asthma, arteriosclerosis, all kinds of lusus naturae, nephropathy, senile cataract, chronic fatigue syndrome, myodystrophy, peripheral neuropathy, etc.
Moreover, caspase-1 is concerned with various inflammatory diseases and those diseases caused by immune disorders, by means of interleukin-1β (IL-1β) production. A lot of diseases are shown to be involved with caspase-1 including inflammatory diseases and autoimmune diseases listed below; inflammatory bowel diseases such as ulcerative colitis, insulin-dependent (type-I) diabetes, autoimmune thyroid diseases, infectious diseases, rejection of an organ transplantation, graft versus host diseases, psoriasis, periodontitis (above, see N. Eng. J. Med., 328, 106 (1993)), pancreatitis (see J. Interferon Cytokine Res., 17, 113 (1997)), hepatitis (see J. Leuko. Biol., 58, 90 (1995)), glomerulonephritis (see Kidney Int., 47, 1303 (1995)), endocarditis (see Infect. Immun., 64, 1638 (1996)), myocarditis (see Br. Heart J., 7, 561 (1995)), systemic lupus erythematosus (see Br. J. Rheumatol., 34, 107 (1995)), Hashimoto's diseases (see Autoimmunity, 16, 141 (1993)), etc.), etc. Experimentally, it is reported that in liver injury model induced by lipopolysaccharide and D-galactosamine, a caspase-1 inhibitor depressed the symptoms, and it is expected that a caspase inhibitor shows an effect in sepsis, ischemic reperfusion and hepatitis gravis (see Am. J. Respir. Crit. Care Med., 159, 1308 (1999)).
It is also shown that cysteine protease is concerned with rheumatoid arthritis. IL-1β is shown to be concerned with this disease (see Arthritis Rheum., 39, 1092 (1996)), and in addition, as autoantibody toward calpastatin (endogenous calpain inhibitor) was found in the serum of the patients, it is considered that increase of calpain activity leads to the cause of diseases.
It is also known that cysteine protease causes a disease symptom by decomposing various proteins which compose the organism.
It is reported that cathepsin B plays a role in decomposing muscular protein in the chronic phase of sepsis (see J. Clin. Invest., 97, 1610 (1996)), and in decomposing muscular protein in myodystrophy model (see Biochem. J., 288, 643 (1992)). And it is also reported that calpain decomposes the myocyte cells protein of myodystrophy patients (see J. Biol. Chem., 270, 10909 (1995)).
In the ischemic reperfusion model, a result is given that calpain causes degeneration of brain tissues by means of degradation of protein kinase C-β (see J. Neurochem., 72, 2556 (1999)) and that a cathepsin B inhibitor inhibits nerve injury (see Eur. J. Neurosci., 10, 1723 (1998)).
In the brain ischemic model, it is known that the degradation of spectrin by calpain causes a damage and function disorder in the neurocyte (see Brain Res., 790, 1(1998)) and it is reported that an IL-1β receptor antagonist relieved the symptoms (see Brain Res. Bull., 29, 243 (1992)).
In myocardial ischemic model it is confirmed that cathepsin B activity increases in the lesion (see Biochem. Med. Metab. Biol., 45, 6 (1991)).
In the experiment utilizing ischemic liver injury model, it proved that necrosis and apoptosis of hepacyte were induced by means of protein-decomposing activity of calpain (see Gastroenterology, 116, 168 (1999)).
Besides, it is known that calpain causes cornea turbid in cataract by means of degradation of crystalline (see Biol. Chem., 268, 137 (1993)) and that in the lesion of contracted gut mucosa model it was confirmed that the activity of cathepsin B, H and L increased (see JPEN. J. Parenter. Enteral. Nutr., 19, 187 (1995)) and it is shown that cysteine protease is a cause of the diseases resulting from such protein degradation.
It has been revealed that cysteine protease is concerned with systemic disorders of organs and tissues by shock.
It is shown that IL-1β is concerned with septic shock and systemic inflammatory response syndrome (see Igakuno Ayumi, 169, 850 (1994)) and besides, it is reported that in endotoxin shock model induced by lipopolysaccharide, a calpain inhibitor prevented circulatory system disorder, disorders of liver and pancreas and acidosis by means of inhibitory effect of activation of nuclear factor κB (see Br. J. Pharmacol., 121, 695 (1997)).
Since it is reported that calpain is concerned with platelet coagulation process and a calpain inhibitor prevented the coagulation of platelets (see Am. J. Physiol., 259, C862 (1990)), it is conceivable that a cysteine protease inhibitor is useful for the disorder by blood coagulation. From the fact that calpain activity increased in the serum of the patients of purpura (thrombocytopenia) resulting from marrow transplantation, it is conceivable that calpain is concerned with the actual disease symptoms (see Bone Marrow Transplant., 24, 641 (1999)). Caspase-1 inhibitor inhibited the apoptosis of blood vessel endothelial cells, which is seen in the early phase of purpura (thrombocytopenia) and is thought to be important for the progression of the pathology afterwards (see Am. J. Hematol., 59, 279 (1998)), so it is expected that a cysteine protease inhibitor makes effect on purpura and hemolytic uremic syndrome.
The effect of cysteine protease and its inhibitor is being investigated in the field of cancer and metastasis of cancer.
Since the proliferations of pancreas cancer cells (see Cancer Res., 59, 4551 (1999)) and acute myeloid leukemia cells (see Clin. Lab. Haematol., 21, 173 (1999)) were inhibited by an inhibitor or receptor antagonist of caspase-1, it is expected that caspase-1 activity is essential for the process of proliferation of tumor cells, and that an inhibitor thereof is effective for these cancers. Cathepsin B activity increased in colon cancer metastasis model (see Clin. Exp. Metastasis, 16, 159 (1998)). Cathepsin K protein expression was recognized in human breast cancer cells and the relationship of cathepsin K and bone metastasis is shown (Cancer Res., 57, 5386 (1997)). Also, a calpain inhibitor inhibited migaration of the cells and it implied the possibility that calpain inhibition may inhibit metastasis of cancer (J. Biochem., 272, 32719 (1997)). From these, a cysteine protease inhibitor is presumed to show an inhibitory effect on the metastasis of various malignant tumors.
As to AIDS (see AIDS, 10, 1349 (1996)) and AIDS-related complex (ARC) (see Arch. Immunol. Ther. Exp. (Warsz), 41, 147 (1993)), it is shown that IL-1 is concerned with the progress of symptoms, so it is conceivable that cysteine protease inhibition leads to an effective therapy of AIDS and its complication.
Some parasites have cysteine protease activity in their body. Cysteine protease in the phagosome of malaria protozoan is an essential enzyme for supplying nutrition of the parasites. A result is given that the inhibitor of cysteine protease shows an inhibitory effect of the proliferation of the protozoan (see Blood, 87, 4448 (1996)). Thus, it is possible to apply the inhibitor of cysteine protease to malaria.
In Alzheimer-type dementia, it is said that adhesion of non-physiological protein called amyloid to brain is deeply involved with nervous function disorders. Cysteine protease has an activity of generating amyloid by decomposing its precursor protein. Clinically, it is shown that cathepsin B is an enzyme that possesses a processing activity of amyloid proteins in the brains of Alzheimer-type dementia patients (see Biochem. Biophys. Res. Commun., 177, 377 (1991)). Also, expressions of cathepsin B protein (see Virchows Arch. A. Pathol. Anat. Histpathol., 423, 185 (1993)), cathepsin S protein (see Am. J. Pathol., 146, 848 (1995)) and calpain protein (see Proc. Natl. Acad. Sci. USA, 90, 2628 (1993)) and increase of caspase-1 activity (see J. Neuropathol. Exp. Neurol., 58, 582 (1999)) were confirmed in the brain lesions. Besides, by the fact that calpain is concerned with the formation of paired helical filaments which accumulate in Alzheimer dementia patients and production of protein kinase C which stabilizes the protein by phosphorylation (see J. Neurochem., 66, 1539 (1996)) and by the knowledge that caspase is concerned with neurocyte death by β amyloid protein adhesion (see Exp. Cell Res., 234, 507 (1997)), it is implied that cysteine protease is concerned with the disease symptoms.
As to Huntington's chorea, cathepsin H activity increased in the patient's brain (see J. Neurol. Sci., 131, 65 (1995)), and the ratio of activated form of calpain increased (see J. Neurosci., 48, 181 (1997)). In Parkinson's diseases, the increase of expression of m-calpain was recognized in the mesencephalon of the patients (see Neuroscience, 73, 979 (1996)) and IL-1β protein was expressed in brain (see Neurosci. Let., 202, 17 (1995)). Therefore, it is speculated that cysteine protease is concerned with the genesis and progress of these diseases.
Besides, in the central nervous system, spectrin degradation by calpain is found in the process of injury on neurocyte observed in the traumatic brain injury model (see J. Neuropathol. Exp. Neurol., 58, 365 (1999)).
In spinal cord injured model it was recognized that in glia cells calpain messenger RNA increased and its activity increased in the lesion and the possibility was shown that calpain had much to do with the degeneration of myelin and actin after injury (see Brain Res., 816, 375 (1999)). And IL-1β was shown to be concerned with the genesis of multiple sclerosis (see Immunol. Today, 14, 260 (1993)). Therefore, it is conceivable that a cysteine protease inhibitor is promising as an agent for the treatment of these nerve-injuring diseases.
Normally, cathepsin S and cathepsin K do not exist in human arterial walls but it was confirmed that they expressed in arterial sclerosis lesion and they had an decomposing activity of alveolus elastica (see J. Clin. Invest., 102, 576 (1998)) and a calpain inhibitor and antisense of m-calpain inhibited the proliferation of human blood vessel smooth muscle cells and it is shown that m-calpain is concerned with the proliferation of smooth muscle (see Arteioscler. Thromb. Vssc. Biol., 18, 493 (1998)), so it is conceivable that a cysteine protease inhibitor is promising for the treatment of blood vessel lesion such as arteriosclerosis, restenosis after percutaneous transluminal coronary angioplasty (PTCA), etc.
It is reported that in liver, cathepsin B is activated in the process of injuring hepatocyte by bile acid (see J. Clin. Invest., 103, 137 (1999)) and so it is expected that a cysteine protease inhibitor is effective for cholestatic cirrhosis.
In lungs and respiratory system, it is shown that cathepsin S is an enzyme that plays a role in elastin degradation by alveolus macrophages (see J. Biol. Chem., 269, 11530 (1994)), so it is probable that cysteine protease is a cause of pulmonary emphysema. And it is also shown that lung injury (see J. Clin. Invest., 97, 963 (1996)), lung fibrosis (see Cytokine, 5, 57 (1993)) and bronchial asthma (see J. Immunol., 149, 3078 (1992)) are caused by production of IL-1β by caspase-1.
It is pointed out that cysteine protease is also concerned with diseases concerning bones and cartilages. Cathepsin K is specifically recognized in osteoclast and it has a decomposing activity against bone matrix (see J. Biol. Chem., 271, 12517 (1996)), so its inhibitor is expected to show an effect against osteoporosis, arthritis, rheumatoidarthritis, osteoarthritis, hypercalcemia and osteometastasis of cancer, where pathologic bone resorption is recognized. And since IL-1β is shown to be concerned with bone resorption and cartilage degradation, and a caspase-1 inhibitor and IL-1β receptor antagonist inhibit the bone resorption and symptoms of arthritis, a caspase-1 inhibitor and IL-1β receptor antagonist are expected to be effective for arthritis (see Cytokine, 8, 377 (1996)) and osteoporosis (J. Clin. Invest., 93, 1959 (1994)). And it is reported that IL-1β is also concerned with osteoarthritis (see Life Sci., 41, 1187 (1987)).
Cysteine protease is involved with production of various hormones. Since increase of messenger RNA of cathepsin S was recognized by stimuli of thytropin on thyroid epitheliocyte strains (see J. Biol. Chem., 267, 26038 (1992)), it is conceivable that a cysteine protease inhibitor is effective for hyperthyrodism.
Since quantity and activity of cathepsin B protein increased in the gingival sulcus liquid of periodontitis patients (see J. Clin. Periodontol., 25, 34 (1998)), it is pointed out that cysteine protease is concerned with periodontitis.
Therefore, it is expected that the compound that possesses the inhibitory activity of cysteine protease is useful as an agent for the prophylaxis and/or treatment of inflammatory diseases (periodontitis, arthritis, inflammatory bowel diseases, infectious diseases, pancreatitis, hepatitis, glomerulonephritis, endocarditis, myocarditis, etc.), diseases induced by apoptosis (graft versus host diseases, rejection of an organ transplantation, acquired immune deficiency syndrome (AIDS), AIDS-related complex (ARC), adult T cell leukemia, hairy cells leukemia, spondylopathy, disorders of respiratory apparatus, arthritis, HIV or HTLV-1 related diseases such as uveitis, virus-related diseases such as hepatitis C, cancer, collagenosis (systemic lupus erythematosus, rheumatoid arthritis, etc.), ulcerative colitis, Sjögren's syndrome, primary biliary cirrhosis, spontaneous thrombocytopenic purpura, autoimmune hemolytic anemia, myasthenia gravis, autoimmune diseases such as insulin dependent (type I) diabetes, diseases accompanying thrombocytopenia (osteomyelodysplasia syndrome, periodic thrombocytopenia, aplastic anemia, spontaneous thrombocytopenia, disseminated intravascular coagulation (DIC), etc.), hepatic diseases such as viral hepatitis (type A, B, C, F, etc.) or hepatitis medicamentosus and cirrhosis, dementia such as Alzheimer's diseases and Alzheimer's senile dementia, cerebrovascular injury, nerve degeneration diseases, adult acute respiratory distress syndrome, infectious diseases, prostatomegaly, hysteromyoma, bronchial asthma, arteriosclerosis, all kinds of lusus naturae, nephropathy, senile cataract, chronic fatigue syndrome, myodystrophy, peripheral neuropathy, etc.), diseases induced by disorders of immune response (graft versus host diseases, rejection of an organ transplantation, allergic diseases (bronchial asthma, atopic dermatitis, allergic rhinitis, pollinosis, diseases induced by house dusts, irritable pneumonia, food allergy, etc.), psoriasis, rheumatoid arthritis, etc.), autoimmune diseases (insulin-dependent (type I) diabetes, systemic lupus erythematosus, Hashimoto's diseases, multiple sclerosis, etc.), disease by degradation various proteins which compose the organism (myodystrophy, cataract, periodontitis, hepatocyte disease by bile acid such as cholestatic cirrhosis, etc.), decomposition of alveolus elastica such as pulmonary emphysema, ischemic diseases (brain ischemia, brain disorders (encephalopathy) by ischemic reperfusion, myocardial infarction, ischemic hepatopathy, etc.), shock (septic shock, systemic inflammatory response syndrome, endotoxin shock, acidosis, etc.), circulatory system disorders (arteriosclerosis, restenosis after percutaneous transluminal coronary angioplasty (PTCA), etc.)), blood coagulation disorders (thrombocytopenic purpura, hemolytic uremic syndrome, etc.), malignant tumor, acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC), parasitic diseases such as malaria, nerve degenerative diseases (Alzheimer-type dementia, Huntington's chorea, Parkinson's diseases, multiple sclerosis, traumatic encephalopathy, traumatic spondylopathy, etc.), pulmopathy such as lung fibrosis, bone resorption diseases (osteoporosis, rheumatoid arthritis, arthritis, osteoarthritis, hypercalcemia, osteometastasis of cancer, etc.), endocrinesthenia such as hyperthyroidism.
On the other hand, what is the most important for inhibitors in inhibiting the activity of proteases is, the special reaction site which interacts with the amino acid residue that is the activity center of proteases. The surrounding structure of the reaction sites are represented by - - - P3P2P1-P1′P2′P3′ - - - , centering peptide binding (P1-P1′) of the reaction site, and at P1 site there exist amino acid residues fitting the substance specificity of proteases which the inhibitors aim. Some reaction sites against cysteine proteases are known, for Example, in the specification of WO99/54317, the followings are described; P1 position against calpain I, II (norvaline, phenylalanine, etc.),    P1 position against calpain I (arginine, lysine, tyrosine, valine, etc.),    P1 position against papain (homophenylalanine, arginine, etc.    P1 position against cathepsin B-homophenylalanine, phenylalanine, tyrosine, etc.),    P1 position against cathepsin S (valine, norleucine, phenylalanine, etc.),    P1 position against cathepsin L (homophenylalanine, lysine, etc.),    P1 position against cathepsin K (arginine, homophenylalanine, leucine, etc.),    P1 position against caspase (aspartic acid).
On the other hand, in the specification of WO 98/49190, it is disclosed that the compound of formula (A) or a pharmaceutically acceptable salt thereof has an inhibitory activity against cysteine proteases,
wherein ZA is a cysteine protease binding moiety;    XA and YA are independently S, O or N, said N being optionally substituted with alkyl or alkenyl optionally substituted with 1–3 halogen atoms, or (C5–C6)aryl, arylalkyl or arylalkenyl optionally comprising 1–3 heteroatoms selected from N, O and S, and optionally substituted with halogen atom, cyano, nitro, haloalkyl, amino, aminoalkyl, dialkylamino, alkyl, alkenyl, alkynyl, alkoxy, haloalkoxy, carboxyl, carboalkoxy, arylcarboxamide, alkylthio or haloalkylthio;    R1A is alkyl or alkenyl optionally substituted with 1–3 halo or hydroxy; alkylamino, dialkylamino, alkyldialkylamino; or cycloalkyl, alkylcycloalkyl, (C5–C12)aryl, (C5–C12)arylalkyl or (C5–C12)arylalkenyl optionally comprising 1–4 heteroatoms selected from N, O and S, and optionally substituted with halo, cyano, nitro, haloalkyl, amino, aminodialkyl, dialkylamino, alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, carboxyl, carboalkoxy, alkylcarboxamide, (C5–C6)aryl, —O—(C5–C6)aryl, arylcarboxamide, alkylthio or haloalkylthio; andwherein at least one of Y or X is N.